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- Hexane 1density = 0.659 g/mL2 and acetic acid 1density = 1.0446 g/mL2 do not form a solution when mixed but separate into distinct layers. A piece of oak wood 1density = 900 kg/m32 is placed inside a test tube containing hexane and acetic acid; sketch how the three substances would position themselves.
Problem 79
Problem 80a
Two spheres of equal volume are placed on the scales as shown. a. Which one is more dense?
Problem 82
A 32.65-g sample of a solid is placed in a flask. Toluene, in which the solid is insoluble, is added to the flask so that the total volume of solid and liquid together is 50.00 mL. The solid and toluene together weigh 58.58 g. The density of toluene at the temperature of the experiment is 0.864 g/mL. What is the density of the solid?
- A thief plans to steal a cylindrical platinum medal with a radius of 2.3 cm and a thickness of 0.8 cm from a jewellery store. If the platinum has a density of 21.45 g/cm³, what is the mass of the medal in kg? [The volume of a cylinder is V = πr²h.]
Problem 83
Problem 84
Saline solution used in hospital contains 0.9% sodium chloride by mass. Calculate the number of grams of sodium chloride in 0.5 gal of saline solution if the solution has a density of 1.01 g/mL.
- A 40-lb container of peat moss measures 14 * 20 * 30 in. A 40-lb container of topsoil has a volume of 1.9 gal. (b) How many bags of peat moss are needed to cover an area measuring 15.0 ft * 20.0 ft to a depth of 3.0 in.?
Problem 85
- A 10.0 g block of gold is hammered into a thin gold sheet which has an area of 150 cm2. Given the density of gold is 19.3 g/cm3, what is the approximate thickness of the gold sheet in millimeters?
Problem 86
- The total rate at which power is used by humans worldwide is approximately 15 TW (terawatts). The solar flux averaged over the sunlit half of Earth is 680 W>m2 (assuming no clouds). The area of Earth's disc as seen from the Sun is 1.28 * 1014 m2. The surface area of Earth is approximately 197,000,000 square miles. How much of Earth's surface would we need to cover with solar energy collectors to power the planet for use by all humans? Assume that the solar energy collectors can convert only 10% of the available sunlight into useful power
Problem 87
- In 2005, J. Robin Warren and Barry J. Marshall shared the Nobel Prize in Medicine for discovering the bacterium Helicobacter pylori and for establishing experimental proof that it plays a major role in gastritis and peptic ulcer disease. The story began when Warren, a pathologist, noticed that bacilli were associated with the tissues taken from patients suffering from ulcers. Look up the history of this case and describe Warren’s first hypothesis. What sorts of evidence were required to establish a credible theory based on it?
Problem 88
- Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (e) When yellow stains in a kitchen sink are treated with bleach water, the disappearance of the stains is due to a chemical change.
Problem 92
Problem 92a
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (a) Air and water are both elements.
Problem 92b
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (b) All mixtures contain at least one element and one compound.
Problem 92c
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (c) Compounds can be decomposed into two or more other substances; elements cannot.
Problem 92d
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (d) Elements can exist in any of the three states of matter.
Problem 92g
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (g) The number 0.0033 has more significant figures than 0.033.
Problem 92i
Judge the following statements as true or false. If you believe a statement to be false, provide a corrected version. (i) Compounds always contain at least two different elements.
Problem 93
You are assigned the task of separating a desired granular material with a density of 3.62 g/cm3 from an undesired granular material that has a density of 2.04 g/cm3. You want to do this by shaking the mixture in a liquid in which the heavier material will fall to the bottom and the lighter material will float. A solid will float on any liquid that is more dense. Using an Internet-based source or a handbook of chemistry, find the densities of the following substances: carbon tetrachloride, hexane, benzene, and diiodomethane. Which of these liquids will serve your purpose, assuming no chemical interaction takes place between the liquid and the solids?
- In 2009, a team from Northwestern University and Western Washington University reported the preparation of a new “spongy” material composed of nickel, molybdenum, and sulfur that excels at removing mercury from water. The density of this new material is 0.20 g/cm³, and its surface area is 1242 m² per gram of material. (c) A 10.0-mL sample of contaminated water had 7.748 mg of mercury in it. After treatment with 10.0 mg of the new spongy material, 0.001 mg of mercury remained in the contaminated water. What percentage of the mercury was removed from the water?
Problem 94
Problem 94b
In 2009, a team from Northwestern University and Western Washington University reported the preparation of a new 'spongy' material composed of nickel, molybdenum, and sulfur that excels at removing mercury from water. The density of this new material is 0.20 g/cm3, and its surface area is 1242 m2 per gram of material. (b) Calculate the surface area for a 10.0-mg sample of this material.
- U.S. 1-cent coin (a penny) has a diameter of 19 mm and a thickness of 1.5 mm. Assume the coin is made of pure copper, whose density and approximate market price are 8.9 g/cm3 and $2.40 per pound, respectively. Calculate the value of the copper in the coin, assuming its thickness is uniform.
Problem 103